×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Rigid Frame Foundations

Rigid Frame Foundations

Rigid Frame Foundations

(OP)
In the design of the drilled shaft to acommodate a long span rigid frame, how is the lateral force handled from the rigid frame reactions, which is substantial?  Do you tie back into the slab or tie the columns together with enough tension reinforcing that the load cancels out?

RE: Rigid Frame Foundations

On foundations for prefabricated metal buildings, I use hairpins into the SOG for small horizontal loads (generally friction of the slab-on-grade against the soil controls), and I use continuous deformed bars through the SOG from one column to the opposite column for large horizontal loads.  For this option, make sure the bars are developed into the drilled pier (you will need hooks).

DaveAtkins

RE: Rigid Frame Foundations

I have designed more rigid frame foundations that I care to admit. Dave Atkins approach is excatly what I used in the past and will continue to use.

Good luck

RE: Rigid Frame Foundations

I agree with Dave as well. We also use Grade beams across the bldg in many cases if the forces are too great for Hairpin/slab solution, However, be aware of any trench drains, etc. that could interfere with reinf. or grade beams.

RE: Rigid Frame Foundations

Just a couple of questions regarding the hair pin solution:

1.  The hair pin solution relies on the floor slab being in place.  In many cases, the metal building is erected, the roof on and in some cases the walls installed PRIOR to pouring the floors.  Hence, the hair pins are not restraining the horizontal thrusts from the wind loads etc. until the floor is poured and up to strength.  How do you justify this?

2.  Besides using the hair pin at each column or a tie rod between columns, the footing/pier can be designed for combined loading to carry both vertical and horizontal loads.  Yes, it becomes a much larger chuck of concrete, but do any of you use this option?

Just some addtional questions on what others are doing.

RE: Rigid Frame Foundations

jheidt, yes. If the slab won't be poured until later, another solution is in order. We have designed the the piers/ftgs to resist thrust forces as well. If the drilled shaft can develop fixity at some point it can be designed to support the vert and lateral forces.  We too have used "huge" chunks of concrete as well as "wing" footings wide enough and deep enough to develop the required passive resistance. (Maybe "wing" footing can be described as the typ. cont. ftg between the columns)

RE: Rigid Frame Foundations

On some very large industrial rigid frame structures that I have seen (high eave heights, and heavy crane loads), and where floor trenches/pits are a factor or could very likely be in the future, a foundation with a pair (or more) of piles in line with the frame/truss span have been used. These piles can be very large, sometimes with bells to resist uplift effects, and in some instances I have even seen battered piles to resist the horizontal loads.

One key thing, if you use ties through the slab, make it clear on the drawings that this is a critical part of the structure design, and that removal of the slab, or cutting (say a trench) across a column line requires consultation with the engineer prior to construction. This at least would protect you from the future owner who say decides to remove the entire slab for some reason, and maybe even replaces it with asphalt paving. If this happens and there are problems with the structure down the road (perhaps not a collapse because passive pressure against the grade-beams/foundation walls may provide some level of lateral resistance), but certainly serviceability problems (a binding bridge crane for example), then you as the designer-of-record should be off the hook for problems caused by this owner, because you made your design concept clear on the drawings.

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members! Already a Member? Login



News


Close Box

Join Eng-Tips® Today!

Join your peers on the Internet's largest technical engineering professional community.
It's easy to join and it's free.

Here's Why Members Love Eng-Tips Forums:

Register now while it's still free!

Already a member? Close this window and log in.

Join Us             Close